Galapagos

The Galápagos Islands are best visited by boat -- to visit several islands.

A land based tour on one island misses the beauty and diversity of the flora and fauna on the other islands which are different on the different islands.

We went with OAT, boating to different islands, taking zodiacs to shore, walking with a guide to see the flora and fauna and snorkeling.

The boat was a live-aboard with 20 visitors plus crew. And the tour was fantastic! They had all the snorkel gear and wet suits. The food on board was excellent. The crew were professional and got us in and out of the zodiacs and our life vests. The guides were very knowledgeable about the flora and fauna. They knew exactly what trails to take because the National Park assigns them what trail to walk and when to go there. I absolutely recommend them.

As I understand it, you will have to go with a guide to visit any of the islands. And once on the island, must stay on the trails, which are rocky and slippery. I'm glad I had hiking poles.

Also, each tour group is limited to a set time period to visit each island. So it is never crowded. We only saw one other tour group on each island we visited.

There is a $200 entrance fee payable in CASH that must be paid at the airport, plus a transit control card (TCT) of $20 that can be paid online. So if you DIY, be prepared to pay these fees.

There is NO car rental on the Galapagos. So if you DIY, you will get around using taxis (typically they are white pickup trucks) to take you to the visitor sites outside of town. you can try to hire them for the day. But limiting yourself to one island is a mistake. You have to visit several islands while you are there and it's only by guided tour.
The towns are small and not really worth visiting, but that's where you would stay if you DIY- or one of the lodges out of town.

Highlights include the Charles Darwin Research station on Santa Cruz Island, the Giant Tortoises at one of the tortoise reserves.
Our tour visited the islands of Floreana, San Cristobal, Santa Fe and Espanola.

Th must-see wildlife are the tortoises, the blue-footed boobies and the marine iguanas.

GO WITH A TOUR GROUP, you'll see more, learn more from the guides a and have less transportation hassle.

In 2019, we did what you want to do, and we loved it. (We were 61 at the time.() Before making our decision, I looked up which birds and animals could be seen on/near which islands and determined that everything we most wanted to see could be seen on a land-based tour. The only thing I would do differently would be to fly both ways between Isla Isabela and Isla Santa Cruz, instead of taking the ferry one way. The ferry trip is truly awful!

Our absolute top snorkelling experience was at Los Tuneles on Isla Isabela. I highly, highly recommend it. I also highly recommend the place we stayed on the island: La Casa de Marita https://www.lacasademarita.com We were also pleased with the company we used to book our day tours/snorkelling excursions: https://book-ec.com

Besides Los Tuneles, another highlight was our day trip to North Seymour Island. The number of birds, especially Blue Footed Boobies and Magnificent Frigate Birds, was astounding! We also loved visiting El Chato Ranch Ecological Reserve, where we could walk among the giant tortoises.

But, really, we loved everything about the trip (except the ferry).

You can read my trip report here, in case you might find it helpful: https://www.safaritalk.net/topic/20536-the-galapagos-may-2019 (I posted the Peru portion of our trip on these forums, but the Galapagos portion at Safari Talk, because it involved so much wildlife viewing.)